The present invention relates to a plasma etching system using a plasma for etching of substrates mounted on a substrate electrode. More specifically, this invention relates to a plasma etching system which uses chlorine gas (Cl2) alone or hydrogen bromide gas (HBr) alone, or a mixture of chlorine gas (Cl2) and oxygen gas (O2) or of hydrogen bromide gas (HBr) and oxygen gas (O2) as an etching gas to provide silicon etching.
A microwave plasma etching system, for example, is known which uses chlorine gas (Cl2) alone or hydrogen bromide gas (HBr) alone, or a mixture of chlorine gas (Cl2) and oxygen gas (O2) or of hydrogen bromide gas (HBr) and oxygen gas (O2) as an etching gas to provide silicon etching.
To prevent substrates from being contaminated by iron (Fe), chromium (Cr) and nickel (Ni), a microwave plasma etching system uses aluminum as the material of the electrode having a ground potential (ground electrode), in place of the material containing these impurities. To prevent the electrode from being damaged or worn by a chlorine gas (Cl2) plasma or hydrogen bromide gas (HBr) plasma, the surface of the aluminum (Al) is further treated with anode oxidation (aluminized treatment). To prevent the substrate electrode from being damaged or worn, the substrate electrode, except for the substrate installation portion, is covered with aluminum oxide (alumina), which acts as a dielectric material.
Prior plasma etching systems do not take into account the metallic contamination by aluminum (Al) generated out of the components of the etching process chamber. Metallic contamination of substrates by aluminum (Al) resulting from etching has occurred in recent highly integrated devices, especially the devices containing minute gates, thereby causing the interface state to be increased.
An object of the present invention is to provide a plasma etching system in which it is possible to avoid metallic contamination by aluminum (Al) as well as metallic contamination by iron (Fe), chromium (Cr) and nickel (Ni), and to suppress device damage.
Aluminum (Al) contamination has been found to be caused by a ground electrode made of aluminum (Al) and the cover (alumina) laid over the substrate electrode, according to an analysis made by the present inventors, namely, according to an evaluation of metallic contamination using total reflection X-ray fluorescence spectrometry.
This shows that the object of the present invention can be achieved by using a ground electrode made of silicon carbide and a cover made of a dielectric material that does not contain aluminum (Al) where the cover is laid over the substrate electrode. This prevents aluminum (Al) from being produced out of these parts.
The present invention is characterized by a plasma etching system comprising a substrate electrode mounted in a vacuum process chamber, a ground electrode and a plasma generating source, wherein plasma is used to provide etching of substrates mounted on the substrate electrode. In accordance with the invention, the ground electrode is made of carbon or silicon carbide, and a dielectric material containing a Si compound covers the surface portion of the substrate electrode facing inside the substrate installation portion of the vacuum process chamber, except for the substrate installation portion itself.
The present invention prevents metallic impurities (Fe, Cr, Ni and Al) from being generated out of the components of the etching process chamber, thereby reducing device damage.